Distributed Applications And Ajax Technology In The Design Of Webgis Applications

There are some problems in current WebGIS System such as weak Data repeated use, feeble Client and relied highly on platform and required improved using new technology. Now, it has changed a lot in compute schema and program design fields, the hot point of distributed compute transforms from traditional schema mainly on distributed OS to practical distributed technology resulted in grid compute platform. Therefore, it which integrated in distributed compute technology becomes the most advanced WebGIS developed pattern. Meanwhile some defaults exist in now WebGIS realized methods, no matter what WebGIS design method based on fat Client and thin Server or fat Server and thin Client, while it that Google maps' success provides a new design solution and schema. At the same time, it has became a tendency of spatial data managed by database due to geography data' mode of storage converts from files' storage to database storage. Sense it is most important to research on a supposing most users operation simultaneous, well safety of system and being independent of Client' WebGIS platform.Analyzing and comparing some WebGIS design modal now, a new system framework based on COM+ and AJAX. This system uses three-tier architecture: GIS function locates in business logical section, pictures from Server are displayed and realized by displayed section and spatial data storage, inquiry and maintenance by using of spatial index and large DBMS exists in data service section. The core of that bases on .NET platform and COM+ and is realized by C Sharp. It is proved that this architecture has advantages of fully using of Server' resources, supposing of users operation simultaneous and highly safety of system contrary to now mainly WebGIS realized methods.